A polyalkylene glycol chain-containing polymer is provided with characteristics such as hydrophilicity, hydrophobicity, and steric repulsion by appropriately adjusting the chain length or alkylene oxides constituting the chain. Such a polymer has been widely used as a soft segment in various applications such as an adhesive or sealing agent application, a flexibility-giving component application, and a detergent builder application.
Recently, an admixture for cement which is added to a cement composition (for example, cement past prepared by adding water to cement, mortar prepared by mixing sand that is a fine aggregate with cement past, concrete prepared by mixing gravel that is a coarse aggregate with mortar) has been investigated as an application of such a polymer. Such an admixture for cement is generally used as a water-reducing agent and the like and expected to exhibit the following functions: the fluidity of the cement composition is improved and thereby the cement composition is water-reduced, and as a result, a strength, a durability, and the like of a cured product of the cement composition are improved.
With respect to a conventional admixture for cement, a naphthalene admixture for cement and a polycarboxylic acid admixture for cement have been known, for example, Japanese Kokai Publication No. 2001-220417 discloses a copolymer for admixtures for cement, obtained by copolymerizing an unsaturated carboxylic acid monomer with an unsaturated polyalkylene glycol ether monomer.
This copolymer for admixtures for cement can provide an admixture for cement which exhibits dispersibility at a certain high level. This is because a carboxyl group derived from the unsaturated carboxylic acid monomer serves as an adsorptive group which adsorbs to cement particles and a polyalkylene glycol chain derived from the unsaturated polyalkylene glycol ether monomer serves as a dispersion group which disperses the cement particles, and further because a steric repulsion of the polyalkylene glycol chain is generated.
However, development of an admixture for cement which can exhibit higher dispersibility has been needed for further reduction in the use amount of the admixture for cement.
Mercapto groups (in other words, a thiol group or a SH group) are functional groups useful for organic synthesis because such groups have a peculiar reactivity. Therefore, a thiol compound containing at least one mercapto group in a molecule has been used in various applications utilizing the peculiar reactivity attributed to the mercapto group. For example, the conventional application fields of the polyalkylene glycol which has been useful as a soft segment in an adhesive or sealing agent application, an application of a component which provides various polymers with flexibility, and the like, are extended. As a result, a thiol-modified polyalkylene glycol obtained by introducing a mercapto group into polyalkylene glycol has been noted.
With respect to a conventional thiol-modified polyalkylene glycol, Japanese Kokoku Publication No. Hei-07-13141 discloses a polyether containing a mercapto group at one or both ends, obtained by adding thiocarboxylic acid to polyether containing a double bond at one or both ends and then decomposing the generated thioester group. Further, Japanese Kokai Publication No. Hei-07-109487 discloses, as a biodegradable water-soluble polymer used in a detergent builder, a polymer obtained by a block or graft polymerization of a monoethylenically unsaturated monomer component with a modified polyether compound obtained by introducing a mercapto group-containing compound into a polyether compound by an esterification reaction.
However, these polymers are not enough to exhibit extremely high cement dispersibility (which is also called as water-reducing property) which has been recently needed. Accordingly, such polymers have room for improvement in order to be preferably used in an application of an admixture for cement and thereby to be useful in much more fields.